| Reinforcement corrosion is the primary reason for the durability performance regression of marine engineering.Many factors will trigger cracks in the concrete which accelerates steel corrosion seriously.It is of great significance for engineering to highlight the quantitative influence of cracks on steel corrosion in concrete as well as development of crack repair technology.Electrochemical impedance spectroscopy was used in order to study corrosion behavior,influence of crack width and reinforced concrete specimens with different crack parameters.The wire beam electrode was utilized to study non-uniform corrosion of reinforcement in cracked mortar.The electrochemical deposition technology was also employed to study the effect of different electrode materials,electrode distances and current densities on crack repair of concrete.The results are as follows:(1)The steel bars are not vulnerable to be affected by the crack which is within 0.15 mm because of its certain self-healing ability.When the crack width exceeds 0.15 mm,the corrosion rate of the steel bar rises with the increasing of concrete crack width.Compared to concrete specimens with single crack,that with double crack are more likely to corrode.Moreover,the smaller crack spacing,the faster the corrosion rate of the steel bars.The concrete specimen with longitudinal crack is more susceptible to corrosion compared with that with transverse crack while with the same width.Corrosion resistant steel bars have better corrosion resistance in marine environments compared with ordinary steel bars.(2)In order to study non-uniform corrosion of reinforcement in mortar with crack width of 0.1mm-0.3mm,the wire beam electrode was exposed to dry-wet cycle in seawater and sodium sulfate solution,seawater immersion environment.The results show that: The non-corroded behavior of steel bars in cracked mortar specimens can be effectively monitored by WBE technology combined with electrochemical impedance spectroscopy.When the crack width is 0.1mm,the electrode corrosion reaction is controlled because the secondary hydration of the cementitious material has a blocking effect on the crack and When the crack is 0.3mm,the corrosive medium such as water,oxygen and corrosive ions are more likely to penetrate and induce corrosion of the electrode.Seawater has a certain repairing effect on micro-cracks but the dry and wet cycle of sodium sulfate will break the mortar and the expand crack width gradually which will eventually lead to the corrosion of electrode.(3)In order to study the effect that different electrode materials,electrode distances,and current densities on the crack repairing of concrete,pre-mixed chloride salt concrete with crack width of 0.3mm was fabricated and seawater was used as electrolyte solution.The distance between the electrode and the concrete ranges from 0-60 mm and the current density varies from 0.25 to 2.0A/m2.The results show that: The content of chloride ions in the concrete after electrodeposited repair is significantly reduced and the ratio of crack closure is the fastest in the first three weeks.The sediments are dominated by Mg(OH)2 and Ca CO3 and the content of Mg(OH)2 is almost three times than that of Ca CO3.When the distance between the electrodes and concrete is less than 20 mm,the ratio of crack closure is high,the crack filling depth is large,and the sediment particles are dense.When the distance is greater than 40 mm,the sediment cannot completely block the crack and the sediment particles are loose while the crack healing effect is poor.When the current density is less than 0.5A/m2,the deposit can effectively block the crack,the water permeability coefficient is small,the sediment particles are dense and the crack repair effect is better;when the current density is greater than 1A/m2,the crack can be quickly healed within 4 weeks,however,the sediment only fills the surface of the crack,and the sediment is loose and porous,and the repair effect is poor. |
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